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Discussion Starter #1
For some reason, the rotors on my 98 900RR keep getting warped. Between the 2nd and 3rd set, I replaced nearly everything, from the forks, lower triple, calipers, pads (galfer hh), axle, wheel, and wheel bearing. I've taken the calipers off, one by one. THe wheel spins freely on the axle. However, when I put the calipers on, the wheel gets tight in a certain range and then spins freely, then tightens up again when it gets to teh same spot. WTF is up? Never had a problem with any of my bikes and I don't do stoppies or anything weird.

Cannot figure out this problem! I was thinking about dropping some $ for some ebc or galfer rotors, but it would be a huge waste of money if they got warped as well.
 

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It sounds like you've been really unlucky. The most likely solution to the problem is that one of the disc buttons is clogged up and stopping the disc from doing its floating bit. take them off and give all of them a squirt with brake cleaner and a polish.
 

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Have you checked the wheel and rotors with a dial gauge?
It's possible the wheel hub or the caliper mounts on the forks or calipers may not be true. Having replaced everything though it seems to be something not purely mechanical.
When setting up a race bike it's a good idea to align the caliper and fork mounts (by filing) so the brake pads lie in perfect alignment with the discs.
 

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Discussion Starter #4
It sounds like you've been really unlucky. The most likely solution to the problem is that one of the disc buttons is clogged up and stopping the disc from doing its floating bit. take them off and give all of them a squirt with brake cleaner and a polish.
hrm, the buttons are on the rotors themselves right? I will try, but now that I believe that the rotors are warped, they aren't going to unwarp yes? I will still give it a try, although I find it highly unlikely that all 3 rotors have had this problem. Also, the issue seems to be with both rotors as I have spun the wheel with one caliper off one caliper on.
 

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Discussion Starter #5
Have you checked the wheel and rotors with a dial gauge?
It's possible the wheel hub or the caliper mounts on the forks or calipers may not be true. Having replaced everything though it seems to be something not purely mechanical.
When setting up a race bike it's a good idea to align the caliper and fork mounts (by filing) so the brake pads lie in perfect alignment with the discs.
I thought about that, perhaps I'll just need to purchase a runout guage. Where exactly would I file? the caliper mounts on the forks or calipers?
 

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Probably both but we're talking fractions of mm's again so you would need precision measuring equipment.
You need to dial-gauge it to determine if the discs are the problem. You may also want to remove the discs, remount the wheel and check the hub faces for run-out as well.
If the discs are bent you can probably straighten them. If they're warped though I doubt there's much you can do as they're generally too thin for machining.
Since you've replaced everything in the front end I doubt it's a problem with any of the components though.
You haven't replaced the master cylinder so it may be a problem there with fluid not returning and causing the brakes to drag until they get hot enough to warp the rotors.
Are you running an OEM brake lever?
Do you ride with you fingers over the lever at all?
How often do you change the front tyre and do you remove the discs to do it?
 

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Discussion Starter #7
Probably both but we're talking fractions of mm's again so you would need precision measuring equipment.
You need to dial-gauge it to determine if the discs are the problem. You may also want to remove the discs, remount the wheel and check the hub faces for run-out as well.
If the discs are bent you can probably straighten them. If they're warped though I doubt there's much you can do as they're generally too thin for machining.
Since you've replaced everything in the front end I doubt it's a problem with any of the components though.
You haven't replaced the master cylinder so it may be a problem there with fluid not returning and causing the brakes to drag until they get hot enough to warp the rotors.
Are you running an OEM brake lever?
Do you ride with you fingers over the lever at all?
How often do you change the front tyre and do you remove the discs to do it?
I guess I forgot to mention I replaced the MC with one from a 03-04 600RR between the 2nd or 3rd set, so the problem was there with the stock 900RR MC. I do use an oem lever and do not ride with my fingers over lever. I change tires with the rotors still on the wheel, but I my tire has lasted over 2 sets of rotors, so I do not think my mechanic dropped the wheel or anything. This problem happens gradually. When I put them on, they feel fine for a couple of months, then I can feel pulsing through the rotors when I brake and it just gets worse from there... :(
 

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Have you replaced the brake hoses? Are they new? Good quality?

If a hose is damaged it can form a blister inside of the hose, as the fluid heats the blister swells and acts as a one way valve. The master can force fluid past blister inside hose, release brakes and fluid slowly returns past blister. You may have the brakes dragging only some of the time.
Get the front wheel up and push the pistons back into the calipers. Use a spring scale to measure haw much pull it takes to start the wheel turning. This is your base measurement.
Now try going out and getting the brakes hot. Come back and Get the front wheel up and see if it drags after applying the brakes hard and holding for 30 seconds or so. Open the bleeders on the calipers and see if the amount of drag has changed. If it did, pump up the brakes again but this time open the bleeder on the master. Same result as first time miss adjusted master, drag didn’t change at all not in hydraulic system, only changed on calipers bleeders, check hoses. Also recheck starting force hot with calipers pushed back to see if slides or caliper pistons are sticking, when calipers are hot.

Remember if a “Vise-Grip” was used on a brake hose it is now junk.
 

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Discussion Starter #9
yes, I replaced the calipers, used goodridge ss lines, and a 600rr master cylinder between the 2nd and 3rd set. I did flush the system with new brake fluid as well.

that info ^ is good to know, however. The pulsing under braking occurs when I first start (cold) to when I get home. I do not think it gets any worse or less throughout the day.
 

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the pulsation is always there once rotors are warped
what we need to find out what is making the rotors warp.
heat , improper torque when installing or cooling unevenly.
 
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